1. Field of the Invention
The present invention relates to a class of locking pliers, or vise grips in general, and more particularly to ground clamp having L-shape clamping arms with holes to attach an insulated U-shape clamping jaw which is connected to the ground cable of an arc welding system and a floating pad attached to a threaded rod so that the effective clamping size is adjustable. Utilizing the U-shape clamping jaw, the present invention is capable of clamping firmly flat workpieces of various thicknesses as well as workpieces with curved or angled surfaces and providing a good electrical conductivity between the ground cable of the arc welding system and the workpiece.
2. Description of the Related Art
A conventional locking plier or vise grip generally comprises a fixed handle, a fixed arm with clamping jaw, a movable handle, a movable arm attached with clamping jaw and a toggling linkage mechanism attached between the movable handle and the fixed handle. In arc welding industry, ground clamps utilizing locking plier mechanism have the advantages of firm contact with the workpiece and quick release after welding. Prior art Welding Ground Clamp by Ronald Brown, U.S. Pat. No. 5,046,958 is one of the example. It shows a locking plier with U-shape fixed arm and U-shape movable arm with flat or curved clamping jaws and ground cable connection on the body of the fixed arm. It has good electrical contact surfaces for flat workpieces and matching cylindrical workpieces, but not for cylindrical workpieces of different diameter and workpieces of other shapes. Another disadvantage of this prior art is the limited opening of the clamping jaws, which limits the thickness of the workpieces that can be clamped. Yet another disadvantage of this prior art is the swing angle of the ground cable is limited to less than 90 degrees, this may cause inconvenience during the welding process. Prior art Quick Releasable Ground and Rod Clamp for Welding by Thomas P. Peviani, U.S. Pat. No. 4,820,901 is another example. It shows a locking plier with long straight fixed arm and long straight movable arm with sharp clamping jaws and ground cable connection on the body of the fixed arm. It has good contact pressure on any shape of workpieces, but it may not have good electrical contact with the workpiece for large current flow because of the small contact area. Another disadvantage of this prior art is the limited opening of the clamping jaws, which limits the thickness of the workpieces that can be clamped. Yet another disadvantage of this prior art is the difficulty in inserting and connecting the ground cable. Yet another disadvantage of this prior art is the single position of the ground cable, that means the cable cannot be positioned at a more convenient position for a particular workpiece under a particular welding environment. It is the intention of the present invention to overcome the above mentioned disadvantages.